The present invention generally relates to a heat exchange system for a fuel delivery system. It finds particular application in conjunction with modern jet aircraft turbine engines and will be described with particular reference thereto. However, it is to be appreciated that the present exemplary embodiments are also amenable to other applications.
Modern jet engine fuel systems utilize a variety of fuel/oil (liquid-to-liquid) heat exchangers to both cool engine and electrical generator lubricating oil, and heat (or cool) portions of the fuel used by the engine as burn flow or for actuation purposes. Typically two fundamental approaches are used in the thermal management of the engine's fluids with regard to heat exchangers to obtain the maximum heat exchange performance with the minimum heat exchanger size. The first approach aims at providing the maximum differential temperature between the two heat exchange medias (i.e. fuel and oil). The second approach aims at providing the maximum amount of flow through the heat exchanger. Both of these approaches work to minimize the physical size and weight of the heat exchanger.
Fundamentally, heat transfer in a heat exchanger follows a relationship that depends on the two major factors as alluded to above. These factors are exchange fluid temperature difference (hereafter ΔT) and a heat transfer coefficient that is highly dependent upon the amount of fluid flow through the heat exchanger. In the typical jet engine application, the two fundamental drivers in heat transfer are not maximized together. That is, maximum ΔT and higher fluid flow rates generally do not accompany one another.
Accordingly, there is a need for an improved heat exchange system for a delivery system for a jet aircraft turbine engine which provides both a maximum ΔT and higher fluid flow rates.